If you get a letter in the mail inviting you to participate in a simple, potentially lifesaving screening to assess your risk for stroke, abdominal aortic aneurysms and other scary stuff, you should probably toss it out with the rest of the junk mail.

Direct-to-consumer screenings are popping up all over. Common tests offered include ultrasounds of the carotid arteries, heart and aorta to look for cardiovascular disease; and blood tests, genetic testing, X-rays and CT scans, among others, all without a recommendation from a doctor.

"Some of these tests are useful and recommended, like blood tests to check cholesterol levels. But others, such as prostate-specific antigen [PSA] testing, are at best controversial at this time. Some tests, such as a heel ultrasound to look for osteoporosis, are simply not recommended and are not the standard of care, yet people can buy this, if it is offered," says Dr. Erik Wallace, associate professor and associate program director with the Department of Internal Medicine at the University of Oklahoma School of Community Medicine in Tulsa.

For those without health insurance, the cost of a direct-to-consumer screening (also called a commercial screening) is likely less than going to a hospital and paying out-of-pocket, so it may be an alternative in some situations, points out Wallace.

There are also potential -- although unproven – benefits. For example, direct-to-consumer screenings can improve patient autonomy and lead to greater transparency and competition in health care. It can also offer more efficient care delivery and improve access to health care, says Dr. Kimberly Lovett, assistant clinical professor of family and preventive medicine at the University of California, San Diego.

"Patient access to care can be impacted by many issues, including lack of insurance, lack of transportation, and time delay in seeing a practitioner. The direct-to-consumer medical marketplace could potentially mitigate each of these access issues if practiced in a medically and ethically responsible manner," she says.

The downsides

But for the few pluses, there is plenty of downside to direct-to-consumer screening tests. For starters, the industry doesn't participate in informed consent discussions -- those conversations where your doctor explains the risks, benefits and alternatives to a particular treatment plan, especially if it is invasive -- provide follow-up care for patients or make judgments about the appropriateness of the screening tests for patients, says Lovett.

Because of this, if a consumer suffers an adverse outcome, it would be difficult to hold the provider accountable. Lovett offers an example: One common service is a heart scan to evaluate for plaque, which most adults have to some degree. Yet the scan generally cannot provide a risk assessment in terms of who will have a heart attack and who will not. A positive result can lead to a significant amount of worry, and more tests. Some of these tests may be as mild as blood analysis, but others may be as serious as unnecessary angiograms and revascularization procedures, says Lovett.

Furthermore, says Lovett, many of the medical screening tests are not supported by evidence-based guidelines and therefore expose patients to tremendous and unnecessary harm. "The data has shown that many of these tests [when used for disease screening] will produce far more harm than benefit for most patients," says Lovett.

Linda Sherry, director of national priorities for Consumer Action, agrees. "These tests have limited or no diagnostic value and may trigger stress [and] fear, and encourage further, more expensive testing to rule out false positives. Insurance won't pay for them unless they are ordered by a doctor for diagnostic reasons, not preventive reasons."

If you're looking to save money, "you can take your own blood pressure at most pharmacy chains and many communities have health screening days designed to educate people about symptoms that might require follow-up," says Sherry.

The perils of self-diagnosis

Worse still, people might buy direct-to-consumer health screenings for their own self-diagnosis and self-treatment for symptoms of disease. "It's difficult for the lay public to really appreciate the nuances and wholly understand the difference between screening and diagnostic testing. Many patients seek screening tests for symptom diagnosis. These patients can be dangerously falsely reassured by normal results if they have chosen the wrong test, or even led in the wrong direction with abnormal results," cautions Lovett.

Wallace says the benefits of the tests are either overstated or misstated. For example, carotid ultrasounds are frequently advertised as a test to help prevent strokes. However, this test has not been proved to be of any benefit for people who do not have symptoms of a blocked carotid artery, says Wallace. Health-screening companies might offer other tests that have proved beneficial, such as an ultrasound for an abdominal aortic aneurysm. But even this test has shown benefit only in men over age 65 who have smoked. Men who are younger or much older, or who have never smoked, should not get this test, says Wallace.

No insurance coverage for DIY health care

While medical screenings are pitched as an inexpensive way to "verify your good health," you'll do so on your own dime. Generally, health insurance does not cover the screenings because there are no proven benefits for some of the tests, says Wallace. "Either the tests themselves are not beneficial for the general population, or the tests are only beneficial to certain people based on age, sex and risk factors," he adds.

While the medical tests may not cost you big bucks, follow-up tests may cost a lot more if the initial test indicates a possible problem. "Although insurance will likely pay for follow up of an initial abnormal test, the patient still must cover co-pays and deductibles," says Wallace.

Consumers hope a simple and inexpensive test can catch something early and lead to an effective treatment or cure. But Wallace says "there's no guarantee you won't get sick, even those who take great care of their health. The best thing any of us can do is to do things that reduce our risk of illness -- eating well, exercising and not smoking. Focus your time and money on this, instead of direct-to-consumer screenings."